Apparatus for grinding a material suspended in a liquid



0d. 20, 1959 H, ssou ETAL- 2,909,334

APPARATUS FOR GRINDING A MATERIAL SUSPENDED IN A LIQUID Filed D80. 8, 1955 v 2 Sheets-Sheet 1 Oct.20, 1959 N, H NILSSON ETAL- 2,909,334

APPARATUS FOR GRINDING A MATERIAL SUSPENDED IN A LIQUID Filed Dec. 8, 1955 I 2 Sheets-Sheet 2 nircd aws P te APPARATUS FOR GRINDING A MA'IERIAL SUSPENDEDINV ALIQUID Nils Gunnar Holger Nilsson, Danderyd, and Karl, Aka

Stridsberg, Vallentnna, Sweden 7 Application December 8, 1955, Serial No. 551,924 Claims priority, application Sweden December 23, 19 54 6 Claims. '(Cl. 241-.46)

This invention relates to an apparatus for grinding and finely dividing a liquid-suspending material, particularly fibrous material such as wood pulp and the like. More particularly the invention relates toan apparatus for such purpose and of the type comprising ,a stationary casing, a rotor mounted in said casing andfhaving an envelope surface forming in its entirety or in part one grinding memher of the apparatus, and a plurality of pressure plates mountcdin said casing outside said'rotor and being pivotable inwardly towards said envelope surface of the rotor to serve as the other grinding member of the apparatus. For this purpose the pressure plates'may suitably be slightly curved to adapt themselves tothecurvature of the'rotor circumference. f I V 1 The invention is based on. the observation that when using a grinding apparatus of the ordinary type for the purpose in question the usually large quantities of liquid which, together with the material to be ground, must pass between the cooperating grinding members, cause a certain reduction in the grinding output and at the same time the apparatus is forced to continue the workingof the already finely divided material beyond what is actually necessary. When treating fibrous material this extension of the treatment results in a shortening of the fibres which is undesirable. If it were possible toremove the material which had acquired the desired degree of fineness from 2,909,334 Patented Oct. 20, 1959 of course, be varied as may also the mounting of and the means for operating the pressure plates, and therefore the invention must not be considered to be limited to the examples shown. Furthermore, for the sake of simplicity, all detailed description of the apparatus casing itself and of the arrangements for driving the rotor are omitted, since information on these points will scarcely be required by those skilled in the art.

In the apparatus shown in Figs, 1 and 2 there is mounted in the casing 1 a cylindrical rotor 2, the circumferential envelope surface of which is rifled as at 2a to serve in its entirety as a grinding member in all the three separate sections or stages I, II and I11 into which the apparatus is divided. The difi'erent stages are separated by radial partition walls 3, 4, 5 and 6 which project to- Wards the rotor from the internal cylindrical wall 1a of the casingl to which they are secured. Each such partition wall is provided with a number of openings 8 corresponding to the number of pressure plates 7 in each stage of the apparatus.

Between each pair of adjacent partition Walls there are arranged three pressure plates 7 in such a manner that their lateral edges 7a slide with a tight fit against the partition walls and the pressure plates are pivoted at one end about pins 9 which extend axially in relation to'the apparatus and are located so close to the outer casing wall 1a that each part of the pressure plate which surrounds the pin 9 also seals against the inside of the outer casing to the required extent. The ends of the pressure plates 7 remote from the pins 9 are provided with a projecting edge 10 which slides with a tight fit against a transverse Wall 11 projecting between the partition Walls, the side of the said transverse 'wall turned towards the pivot pin 9 of the related pressure plate being somewhat concave in order to follow through an arc with the pin as its centre.

the machine in the meantime-the working results would T be more uniform and atthe same time a reduction ;in the energy consumption of the machinexwould beobtained.

The present invention has for its object to provide an apparatus by means :of which this is possible. The'apparatus according to the invention is mainly characterized by. the fact that'the pressure plates are perforated, as known per se, to enable them to serve as straining members for thematerial treated in the apparatus, and at the same time they "are adapted to serve as confining members demarcating chambers in the apparatus which are provided with outlets through which the liquid and readyground material can flow out.

To enable the invention to be more clearly understood, two embodiments of the apparatus will now be described with reference to the accompanying drawings in which Fig. 1 shows one grinding apparatus according to the invention in longitudinal section; I

Fig. 2 is a cross-section of the apparatus of Fig; 1 taken along line 2 2 in Figure 1;" a

Fig. 3 shows another grinding apparatus according to the invention in longitudinalsection;

Fig. 4 is a cross-section oftheapparatus of Fig. 3, taken along line 4-4 in Figure 3. f

Both apparatus shown in the drawings are intended to t e t t ria n number o a s which re sim a in principle to one another and only differ from each other by the fact that the diiferent pressure plates are pressed against the rotor with varying force and they may also be provided with straining perforations of different sizes. The number of pressure plates in each stage may,

The pressure plates 7 thus separate chambers 12 in the casing 1 from therest of the interior of the apparatus and from these chambers the openings 8 pass out from conducting the ground material to the next stage of the apparatus or for discharging it from the last stage of the apparatus. The pressure plates in the diiferent stages are angularly displaced in relation to one another so that the openings 8 through which the material fiows out from one stage debouch between two successive pressure plates in the next stage, as indicated by dotted lines in Fig. 2.

The pressure plates 7 are perforated as shown at 719 in order to serve as straining members and allow the liquid and already finely divided material to pass through, the said material thereby passing the chambers 12 on its way out of the stage. a e

The pressure plates '7 are tensioned in the direction towards the rotor with the help of a hydraulic pressure medium which is introduced into cylinders 14, one for each pressure. plate, arranged on the outside of the casing and containing pistons 15 connected to the respective pressure plates 7 in any suitable manner permitting articulation, such as by piston rods 15a. The clearance desired between the pressure plates and the rotor 2 may be set by adjusting the-nuts .16 which are threaded on to bolts 17 secured to the respective pressure I even if the,casing 20 cor-responds in; general to the casing Land-also second. apparatus is :arranged' ;to.treat the material in three stages, I, 11 and HI. In the apparatus according to Figs. 3 and 4 the rotor is divided up into three axially spaced portions, one for each stage, the said portions being mounted on a common driving shaft 21. Since the different stages substantially correspond to one another, only one of them will be described, as in connection with the preceding embodiment, whereafter it will be obvious to those skilled in the art how the apparatus-worksas a whole. I V

The rotor portion included in each stage which is generally designated by 22 consists of two circular plates 23 and 24 which are held together by perforated walls 25 which extend substantially spirally from the shaft 21, and serve as a sort of impeller blades, which during the clockwise rotation of the rotor feed out material from the centre of the rotor portion concerned, into which the material is admitted through an opening 26 in plate 23, to the periphery of the rotor where each of the partition walls 25 merges into a rifled, at 27a, unperforated rotor sdle 27 which extends between the plates 23 and 24 in a backward direction from the partition wall 25 reckoned in the direction of rotation of the rotor. The parts or soles 27 of the rotor envelope form together one grinding member of the apparatus. From the rear end of each sole 27 a demarcating plate 28 extends in a curved shape towards the inner end of the corresponding partition wall 25 and thus, together with the partition wall 25 and the rotor sole 27, bounds a substantially triangular chamber 29 which is provided with an outlet hole 30 in the circular plate 24 located on the feed-out side of the stage.

Thanks to the illustrated construction of the rotor portion, not only will the material be fed from the central intake out to the periphery of the rotor by the impeller action of the partition walls 25 but at the same time a straining of a certain part of the liquid and already finely divided material will take place through the perforated walls 25, and the strained liquid, etc. will pass through the chambers 29 and out through the holes 30 to pass on to a subsequent working stage in the apparatus. This preliminary straining in the rotor part has been found surprisingly effective, which may be explained by the favourable conditions of flow past the surface of the strainer.

Each rotor portion 22 cooperates with a corresponding stator portion forming part of the stationary casing and consisting each of two flanges 32 and 33 projecting radially inwards from the casing and being coplanar with the two circular plates 23 and 34 respectively of the related rotor portion. The radially inner edges of said flanges tightly abut the radially outer edges of the rotor plates so that none of the material treated may leak out between them. Between the flanges 32 and 33 a numberfour shown in the drawingof perforated pressure plates 34 bent in accordance with the rotor periphery are arranged which, together, entirely surround the rotor. Each of the pressure plates 34 has its lateral edges in substantially fluid-tight .but slidable engagement with the flanges 32 and 33 and its ends in substantially fluid-tight contact with the adjacent pressure plates in the stage. Each prasure plate 34 has rigidly secured to its outside an extra wall structure 35 forming a box-shaped attachment the side walls of which are formed by the flanges 32 and 33: Also the walls 35 have their lateral edges in sliding, fluid-tight engagement with the flanges 32 and 33. Each of the pressure plates provided with such a box-shaped attachment is hingedly connected at one end to the casing 1 through a link member 36 and is therefore capable to move slightly between the flanges 32 and 33 radially away from the rotor 22 to let in material between the rotor soles and the respective pressure plates. On the other hand, the space 37 externally of the walls 35 on the pressure plates but inside the casing 20 forms a pressure chamber into which a liquid under pressure, such as water, can be introduced through inlets 38 to rotor. A slight leakage of liquid resulting from this arrangement is of no importance in practice when the material treated in the apparatus is suspended in the same liquid as that introduced through the inlets 38.

Simultaneously with the grinding operation in this apparatus straining out of the liquid and finely divided material through the perforations in the pressure plates 34 takes'place, and the strained material, etc. passes through the interior of the box-like attachments under the walls and out through holes 39 in the flange 33 which is located on the outlet side of the stage. The holes 39 are, of course, so located that they are always between the pressure plates 34 and the external confining wall 35 of the attachments.

What we claim is:

1. An apparatus for grinding a liquid-suspended material, particularly a fibrous material such as wood pulp and the like, comprising a stationary casing, a rotor mounted in said casing, circumferentially located, rough surfaces on said rotor forming the one grinding member of the apparatus, a plurality of concave pressure plates hingedly mounted in said casing outside said rotor, means for pressing said pressure plates towards said rough surfaces of the rotor so as to form the other grinding member of the apparatus, said pressure plates being perforated to serve as straining members for the material treated in the apparatus, spaced outlet chambers inside said casing and radially outside each of said perforated pressure plates, each such outlet chamber communicating with the rest of the interior of the apparatus through said perforated pressure plates, and outlets in said chambers to discharge such liquid and ready-ground material which has passed through the perforations of said pressure plates.

press against the outer side of the attachment walls 35,

and hence press the related pressure plates against the 2. An apparatus according to claim 1, wherein the pressure plates are provided with attachments which slidably and in a substantially fluid-tight manner engage portions of the stationary casing, the latter being provided with inlet openings for a pressure medium acting on the outside of the attachments to force the pressure. plates towards the rotor.

3. An apparatus according to claim 1, wherein there is a central inlet and wherein the rotor is constructed in the form of an impeller with blade-forming portions to feed material from said central inlet towards the pressure plates, the blade-forming portions of the impeller being perforated and arranged to confine additional straining chambers in the rotor, said chambers having outlets in open communication with the outlets of said' spaced outlet chambers.

4. An apparatus according to claim 1, wherein said stationary casing has inwardly extending radial wall portions and wherein each perforated pressure plate has lateral edges in sliding, substantially fluid-tight engagement with opposed ones: of said wall portion, sealing means being provided between the ends of each pressure plate and said casing to form therewith an outlet chamber of variable volume.

5. An apparatusaccording to claim 1, wherein said outlet chambers are formed between the radially outer side of each perforated pressure plate and an imperforate extra wall forming a laterally open box-like attachment onthe outside of the related pressure plate.

6. An apparatus according to claim 1, wherein the pressure plates are pivotally mounted in the stationary casing by means of link members.

References (lited in the file of this patent UNITED STATES PATENTS 2,679,788 Skardal June 1. 1954 

